The present invention relates to biosensors and more particularly to coplanar waveguide biosensors configured to detect molecular or cellular events.
A number of bioelectric sensors are known in the biotechnical arts and use electronic signals to detect and identify the structure and interactions of molecules, as well as cellular function and activity. In the past, bioelectric sensors (“biosensors”) typically have been constructed in a parallel-plate capacitor device in which layers of probes are immobilized on of the opposing surfaces between the capacitor plates. The sought targets have a high binding affinity for the probes and, when captured onto the plate surface, operate to change the capacitance of the biosensor. The change in capacitance can be measured by passing an electronic signal (typically a time-varying ac signal of relatively low frequency) between the two capacitor plates before and after binding and comparing the respective responses. Examples of these types of biosensors are disclosed in U.S. Pat. No. 5,653,939 to Hollis et al., as well as U.S. Pat. No. 5,187,096 to Giaever et al. which discloses a similar structure for cell-based measurements.
The capacitor-type biosensor suffers from some disadvantages, one being the relatively low frequency range over which the biosensor can be used. Typically, the measured cells or molecules situated between the plates will reside in an aqueous environment which significantly attenuates signals propagating between the two plates. As a result, the highest frequency signal measurements are typically in the high KHz region to low MHz. As recent developments in the laboratories of the present inventors have demonstrated, a significant amount of information can be obtained by interrogating molecular and cellular activity at both these commonly used frequencies and at higher frequencies. An improved biosensor capable of operation over a broader range of frequencies would therefore be advantageous.